git: 628d378aaa4e - stable/15 - bsd.sys.mk: Silence a few GCC warnings for C++

The branch stable/15 has been updated by jhb:

URL: https://cgit.FreeBSD.org/src/commit/?id=628d378aaa4e1d1ff132cdac518e131922759352

commit 628d378aaa4e1d1ff132cdac518e131922759352
Author:     John Baldwin <jhb@FreeBSD.org>
AuthorDate: 2026-01-27 18:39:05 +0000
Commit:     John Baldwin <jhb@FreeBSD.org>
CommitDate: 2026-04-24 15:26:39 +0000

    bsd.sys.mk: Silence a few GCC warnings for C++
    
    These warnings were already marked with -Wno-error=, but they trigger
    so many false positives in libc++ headers to be utterly useless for
    C++ code, so disable them entirely for C++.
    
    Reviewed by:    imp, dim
    Differential Revision:  https://reviews.freebsd.org/D54867
    
    (cherry picked from commit 6fb87a1a6042887550571316fa9e539239f158d1)
---
 share/mk/bsd.sys.mk | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/share/mk/bsd.sys.mk b/share/mk/bsd.sys.mk
index 8ca3fd21c616..d58830ad48c7 100644
--- a/share/mk/bsd.sys.mk
+++ b/share/mk/bsd.sys.mk
@@ -190,6 +190,11 @@ CWARNFLAGS+=	-Wno-error=address			\
 		-Wno-error=uninitialized		\
 		-Wno-error=unused-function		\
 		-Wno-error=unused-value
+
+# These warnings are raised by headers in libc++ so are disabled
+# globally for all C++
+CXXWARNFLAGS+=	-Wno-attributes				\
+		-Wno-deprecated-declarations
 .endif
 
 # GCC 6.1.0
@@ -243,6 +248,7 @@ CWARNFLAGS+=	-Wno-error=overflow
 # globally for all C++
 CXXWARNFLAGS+=	-Wno-literal-suffix			\
 		-Wno-c++20-extensions			\
+		-Wno-attributes				\
 		-Wno-error=unknown-pragmas
 .endif